Project Summary Diversion of ADHD stimulants, by sharing, selling, or trading, is the primary conduit by which these Schedule II controlled drugs reach their peak prevalence of misuse in early adulthood (use without a prescription, overuse of prescribed medication). Yet, understanding of stimulant diversion and contributing factors is limited to speculation from small cross-sectional studies. Dramatically increased rates of stimulant prescribing in recent years (from ~49.2 to 62.8M people), mainly in adults, has heightened concern. The state- of-science on this important topic precludes development of prevention efforts based on variables with inferred causal influence. Additionally, although primary care is the most common treatment setting for ADHD, this population and its risk for diversion in adulthood, including when diagnosis and treatment occurs after childhood, is poorly understood. Due to concern about these trends and reports of associated physical dangers and legal consequences, the FDA recently established a public docket requesting comments on the potential role of abuse- deterrent stimulant formulations. The accompanying review stated a need for information on factors that would inform their decision-making, including characterization of longitudinal pathways to misuse. The proposed study prospectively examines stimulant diversion and hypothesized risk factors among young adults at peak age for stimulant diversion: those initially diagnosed and stimulant-treated in early adulthood, and those stimulant-treated as adolescents by pediatricians and aging now into early adulthood. The combined sample will provide a unique opportunity to examine associations between timing of ADHD treatment, stimulant diversion, and hypothesized risk factors. N=357 adolescents stimulant-treated for ADHD in primary care (U01 DA040213), and 150 newly recruited young adults first diagnosed and treated in adulthood, will be studied (total n = 507). Three annual assessments will span ages 18-24 to allow prospective study of stimulant diversion during the age period of its greatest prevalence. Self- and parent-report and behavioral economics tasks will be used to assess intrapersonal, attitudinal-behavioral, and social-normative risk factors and environmental moderators (parenting and provider factors). The results of this study will aide Priority Focus Area #3 of NIDA?s 2016-2020 Strategic Plan, ?Addressing Real World Complexities? by generating findings that will apply to two of the largest, least understood segments of the treated ADHD population?those treated in primary care, and those young adult-diagnosed. Findings will provide crucially needed prospectively gathered data to inform the development of stimulant diversion prevention efforts.